The present invention relates to an ultrasonic driving device comprising a stator consisting of a cylindrical piezoelectric vibrator having divided electrodes.
In a known ultrasonic motor using a piezoelectric vibrator, two groups of electrodes are attached to one end of a ring type piezoelectric ceramic, the two group of electrodes are so positioned that standing waves respectively generated by the two groups of electrodes are lifted every .pi./2 in each position. The parts of the ring type piezoelectric vibrator corresponding to the electrode are alternately polarized in reverse. Also, the two groups of the electrodes are respectively connected to two oscillators for respectively generating alternating current voltages having a .pi./2 phase shift from each other. When the alternating current voltages from the two oscillators are respectively applied to the two groups of electrodes, the two standing waves having a .pi./2 phase shift from each other generated on the surface of the ring type piezoelectric vibrator and then progressive waves owing to a compound of the two standing waves generated on the surfaces of the ring type piezoelectric vibrator. Therefore, when a rotary member is put on the ring type piezoelectric vibrator and the rotary member is strongly pressed to the ring type piezoelectric vibrator, the rotary member is rotated by the progressive waves.
In prior ultrasonic motor, since the the ring type piezoelectric vibrator must be polarized in many portions thereof and the two oscillators must be connected to the electrodes, the composition of the ring type piezoelectric vibrator is complex and the cost of the ultrasonic motor becomes expensive.